• adhesives
• composites
• Fatigue
• size effect
• standard geometry

This study investigates the influence of specimen geometry on the static and fatigue performances of two bulk epoxy adhesives: Sikadur 330, primarily used in civil engineering, and SikaPower 830, employed in wind turbine applications. It examines ASTM D638-22 Type I, II, and IV specimen geometries. The research also describes the specimen manufacturing process highlighting the challenges. The experimental campaign includes low displacement rate tensile tests, high force-rate tests, and extensive fatigue characterization from 10^3 to 10^6 cycles. Results comprehend S-N curves and employ Digital Image Correlation (DIC) for stress-strain analysis, hysteresis loops, mean strain evolution, and stiffness degradation. The study integrates quasi-static and fatigue results using the Sendeckyj wear-out model for a comparative evaluation across geometries, in addition, Finite Element Analysis (FEA) is used to better study this phenomenon. All the results confirm that different geometries lead to different results, indicating that Type II specimens outperform Type I in tensile and fatigue resistance, with Type IV specimens showing even greater superiority. This underscores the conservative nature of using Type I data in design phases and advises against mixing Type I and II data, despite standard recommendations for transitioning geometries in case of Type I improper failures.